1. Field of the Invention
The present invention relates to well plug additives, to well plug treatment fluids made therefrom, to methods of plugging a well. In another aspect, the present invention relates to well plug additives comprising polymer and fibers or comminuted plant materials, to well plug treatment fluids made therefrom, to methods of plugging a well using such fluids.
2. Description of the Related Art
Wells employed in the production of oil and gas are abandoned inter alia because they reach the end of their useful life or they become damaged beyond repair. State and federal regulations require that abandoned wells be plugged to protect safety and environmental interests. The well is commonly plugged by pumping Portland cement into the wellbore and curing the cement in situ.
Formulation of Portland cement in the field is largely a product of trial and error by field personnel to meet irregularities in the cementing composition and the downhole environment. Cement quality control is difficult to achieve under such conditions. As a result, Portland cement cured in situ can exhibit cracking, shrinking, or poor adhesion to wellbore tubulars. An imperfect Portland cement plug can enable undesirable fluid flow through the wellbore via leaks along or through the cement.
U.S. Pat. No. 4,730,675, issued Mar. 15, 1988 to Wygant and Sydansk note that a process was then needed which employed a plugging material having a broad range of highly controllable and predictable set-up times providing ease of operation and design at a relatively low cost. Wygant and Sydansk further noted that a process was then needed employing a substitute material for Portland cement in conventional plugging processes which forms a more effective plug and seals the wellbore indefinitely.
U.S. Pat. No. 4,730,675 proposes the use of a water soluble carboxylate crosslinking polymer along with a chromic carboxylate complex crosslinking agent in the plugging of an abandoned well, and at column 1, lines 61-63, specifically teaches away from the use of solids in the plugging fluid injected into the wellbore.
Thus, while U.S. Pat. No. 5,377,760, issued Jan. 3, 1995 to Merrill discloses addition of fibers to an aqueous solution of partially hydrolyzed polyacrylamide polymer, with subsequent injection into the subterranean to improve conformance, the performance requirements of conformance improvement treatment polymers are so different from those of polymers for plugging an abandoned well, that such would not necessarily work for well plug treatment. Furthermore, Wygant and Sydansk teach away from injection a solid containing polymer into the wellbore to plug an abandoned well.
Additionally, Merrill's conformance treatment method of mixing the fibers with the polymer solution followed by injection, requires a multiplicity of storage and mixing tanks, and a metering system which must be operated during the operation of the well. Specifically, a first tank will store a water and polymer solution, a second tank will store a water and cross-linking solution, and a third tank will be used to mix fibers with polymer solution from the first tank to create a polymer/fiber slurry. This polymer/fiber slurry is then metered from the third tank and combined with cross-linking solution metered from the second tank to the well bore.
Thus, in spite of the advancements in the prior art, there still is a need for further innovation in the well plug additives.
There is need for further innovation for well plug additives utilizing a water soluble polymer.
There is another need for a well plug additive which would allow for simplification of the mixing equipment.
These and other needs in the art will become apparent to those of skill in the art upon review of this specification, including its drawings and claims.